The present invention relates to plastic containers, and more particularly to plastic containers for holding carbonated or like products that expand after sealing or capping.
Plastic bottles are in widespread use for containing beverages and food products. A particular type of bottle, which is filled with products at elevated temperatures, is designed to accommodate internal vacuum pressure developed upon cooling of the products after sealing. Often, hot fill bottles include panels formed in the container sidewall that inwardly flex or deform in response to formation of an internal vacuum. For example, U.S. Provisional Patent Application No. 60/295,911, filed Jun. 4, 2001, entitled xe2x80x9cHot-Fillable Container With Gripxe2x80x9d discloses a bottle in which inward, vacuum-induced deformation is distributed outside of the handgrip panel.
Another type of plastic bottle that contains carbonated beverages (or like products that exhibit increased internal bottle pressurexe2x80x94that is, compared with the internal pressure upon or soon after capping or sealing) is designed to accommodate internal positive pressure (that is, pressure greater than the ambient atmosphere). Such bottles, which will be referred to herein as xe2x80x9cpressurized bottles,xe2x80x9d are typically formed of blow-molded PET that is capable, upon orienting, of containing an internal bottle pressure of several atmospheres, which may occur when carbonated contents within a bottle are exposed to elevated temperatures, such as 100 degrees F. to 120 degrees F. Such temperatures may be encountered during storage or during transport while the bottle is not in an air-conditioned environment, or like circumstances.
Plastic bottle production is, of course, a competitive industry in which weight-reducing techniques produce significant costs savings, especially in light of the vast quantity of bottles produced worldwide. However, the high internal pressures that pressurized bottles must contain provides a constraint against bottle weight reduction.
U.S. Pat. No. 6,176,382, entitled xe2x80x9cPlastic Container Having Base with Annular Wall and Method of Making the Same,xe2x80x9d discloses a conventional beer bottle shape that may be subject to high internal pressures due to the carbonated (or otherwise pressurized, such as for example by nitrogen) beverage contained therein being exposed to elevated temperature. In this regard, as in most conventional beer bottles and many other pressurized bottles, the exemplary bottle 110 shown in FIG. 7 (PRIOR ART) has a tapered neck 112 extending above a right circular body 116. A shoulder 118 is disposed between neck 112 and body 116. A label panel 120 is defined by at least a portion of body 116. Neck 112 may also receive a label (not shown in the Figures).
Neck 112 has a continuous taper so as to form a frustum of a right circular cone. In this regard, a neck diameter D-PA1 near an upper end of neck 12 is less than a diameter D-PA2 near a lower end of neck 12. Another conventional glass bottle shape (not shown in the Figures) has an upper neck diameter that is the same as the lower neck diameter such that the neck substantially forms a cylinder having a circular cross section. In this regard, the term xe2x80x9cstraightxe2x80x9d or xe2x80x9cstraight portionxe2x80x9d will be employed to refer to a sidewall or a sidewall portion, respectively, that is rectilinear or not curved in longitudinal cross section.
Referring again to FIG. 7, the straight sidewalls of neck 112 and body 116 deform in response to an increase in internal pressure, as indicated diagrammatically by the dashed lines in FIG. 7. The maximum radial expansion is indicated by xcex94-PA-neck and xcex94-PA-body, respectively. Typically, the volumetric expansion of the neck is less than the volumetric expansion of the body and/or the base.
Often, a plastic bottle is developed to replace a corresponding glass container with economic advantages that are apparent. In some circumstances, technical problems must be solved to make a plastic bottle that is commercially satisfactory. For example, a plastic bottle containing a carbonated (or otherwise pressurized) product inherently yields more than a corresponding glass container in response to an increase in internal pressure. Thus, a label panel of a plastic pressurized bottle may deform in response to an increase in internal pressure. Such label panel expansion is undesirable for aesthetic reasons and because the label may tend to separate from the label panel. Further, the bottle base may tend to bulge or xe2x80x9croll outxe2x80x9d in response to such internal pressure, thereby making the base unstable.
In order to produce a bottle that is sufficiently strong to withstand such internal pressure without unacceptable label expansion and/or base expansion or roll-out, bottles formed of oriented thermoplastic are designed with a sidewall and base of sufficient thickness and weight. In general, there is a need for pressurized bottles that have improved expansion characteristics, and/or reduced weight.
A bottle is provided that includes a neck that expands volumetrically in response to an increase in internal bottle pressure. In this regard, such a plastic container comprises a body, a base extending from the body and enclosing a lower end of the container, a finish disposed at an upper end of the container, and a neck disposed between the finish and the body. The neck includes an outwardly convex portion that radially expands in response to positive internal pressure, whereby the maximum magnitude of the radial expansion is less than a maximum magnitude of radial expansion for a frusto-conical neck of like dimension.
Further, the bottle may include a waist that is outwardly concave such that the convex portion of the neck extends upwardly from and smoothly yields from the waist. Thus, the waist may form a hinge point relative to the convex portion. According to another aspect, the neck""s convex portion expansion may diminish expansion of the body straight sidewall, thereby enhancing the appearance and adherence of the label. Also, such expansion may enable the total weight of the bottle to be reduced.